2 * Copyright (c) 2003-2005 The Regents of The University of Michigan
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28 * Authors: Erik Hallnor
32 * Definitions of a simple cache block class.
35 #ifndef __CACHE_BLK_HH__
36 #define __CACHE_BLK_HH__
40 #include "sim/core.hh" // for Tick
41 #include "arch/isa_traits.hh" // for Addr
42 #include "mem/request.hh"
45 * Cache block status bit assignments
47 enum CacheBlkStatusBits {
48 /** valid, readable */
50 /** write permission */
52 /** dirty (modified) */
56 /** block was referenced */
58 /** block was a hardware prefetch yet unaccessed*/
59 BlkHWPrefetched = 0x20
63 * A Basic Cache block.
64 * Contains the tag, status, and a pointer to data.
69 /** The address space ID of this block. */
71 /** Data block tag value. */
74 * Contains a copy of the data in this block for easy access. This is used
75 * for efficient execution when the data could be actually stored in
76 * another format (COW, compressed, sub-blocked, etc). In all cases the
77 * data stored here should be kept consistant with the actual data
78 * referenced by this block.
81 /** the number of bytes stored in this block. */
84 /** block state: OR of CacheBlkStatusBit */
85 typedef unsigned State;
87 /** The current status of this block. @sa CacheBlockStatusBits */
90 /** Which curTick will this block be accessable */
94 * The set this block belongs to.
95 * @todo Move this into subclasses when we fix CacheTags to use them.
99 /** Number of references to this block since it was brought in. */
104 * Represents that the indicated thread context has a "lock" on
105 * the block, in the LL/SC sense.
109 int cpuNum; // locking CPU
110 int threadNum; // locking thread ID within CPU
112 // check for matching execution context
113 bool matchesContext(Request *req)
115 return (cpuNum == req->getCpuNum() &&
116 threadNum == req->getThreadNum());
120 : cpuNum(req->getCpuNum()), threadNum(req->getThreadNum())
125 /** List of thread contexts that have performed a load-locked (LL)
126 * on the block since the last store. */
127 std::list<Lock> lockList;
132 : asid(-1), tag(0), data(0) ,size(0), status(0), whenReady(0),
137 * Copy the state of the given block into this one.
138 * @param rhs The block to copy.
139 * @return a const reference to this block.
141 const CacheBlk& operator=(const CacheBlk& rhs)
148 whenReady = rhs.whenReady;
150 refCount = rhs.refCount;
155 * Checks the write permissions of this block.
156 * @return True if the block is writable.
158 bool isWritable() const
160 const int needed_bits = BlkWritable | BlkValid;
161 return (status & needed_bits) == needed_bits;
165 * Checks that a block is valid (readable).
166 * @return True if the block is valid.
170 return (status & BlkValid) != 0;
174 * Check to see if a block has been written.
175 * @return True if the block is dirty.
177 bool isModified() const
179 return (status & BlkDirty) != 0;
183 * Check to see if this block contains compressed data.
184 * @return True iF the block's data is compressed.
186 bool isCompressed() const
188 return (status & BlkCompressed) != 0;
192 * Check if this block has been referenced.
193 * @return True if the block has been referenced.
195 bool isReferenced() const
197 return (status & BlkReferenced) != 0;
201 * Check if this block was the result of a hardware prefetch, yet to
203 * @return True if the block was a hardware prefetch, unaccesed.
205 bool isPrefetch() const
207 return (status & BlkHWPrefetched) != 0;
211 * Track the fact that a local locked was issued to the block. If
212 * multiple LLs get issued from the same context we could have
213 * redundant records on the list, but that's OK, as they'll all
214 * get blown away at the next store.
216 void trackLoadLocked(Request *req)
218 assert(req->isLocked());
219 lockList.push_front(Lock(req));
223 * Clear the list of valid load locks. Should be called whenever
224 * block is written to or invalidated.
226 void clearLoadLocks() { lockList.clear(); }
229 * Handle interaction of load-locked operations and stores.
230 * @return True if write should proceed, false otherwise. Returns
231 * false only in the case of a failed store conditional.
233 bool checkWrite(Request *req)
235 if (req->isLocked()) {
236 // it's a store conditional... have to check for matching
238 bool success = false;
240 for (std::list<Lock>::iterator i = lockList.begin();
241 i != lockList.end(); ++i)
243 if (i->matchesContext(req)) {
244 // it's a store conditional, and as far as the memory
245 // system can tell, the requesting context's lock is
252 req->setExtraData(success ? 1 : 0);
256 // for *all* stores (conditional or otherwise) we have to
257 // clear the list of load-locks as they're all invalid now.
264 #endif //__CACHE_BLK_HH__